A radar wind sonde also called a radiosonde as used herein comprises a battery-powered telemetry instrument carried into the atmosphere typically by a weather balloon that measures various atmospheric parameters and transmits them by a radio frequency (RF) link to a ground-based receiver. Modern radiosondes measure or calculate environmental variables including altitude, pressure, temperature, relative humidity, wind (both wind speed and wind direction), cosmic ray readings at high altitude, and geographical position (latitude/longitude). Radiosondes are an essential source of meteorological data, and hundreds are launched all over the world each day.
Radiosondes may operate at an RF frequency of 403 MHz or 1,680 MHz. A radiosonde whose position is tracked as it ascends that provides wind speed and direction information is called a radar wind-sonde (or rawinsonde). Most radiosondes have radar reflectors for tracking and are technically radar wind-sondes. A radiosonde that is dropped from an airplane and falls rather than being carried by a balloon, is called a dropsonde.